U.S. patent application number 12/350500 was filed with the patent office on 2009-10-22 for radiation image converting panel.
This patent application is currently assigned to HAMAMATSU PHOTONICS K.K.. Invention is credited to Gouji Kamimura, Jun SAKURAI, Ichinobu Shimizu.
Application Number | 20090261254 12/350500 |
Document ID | / |
Family ID | 41200330 |
Filed Date | 2009-10-22 |
United States Patent
Application |
20090261254 |
Kind Code |
A1 |
SAKURAI; Jun ; et
al. |
October 22, 2009 |
RADIATION IMAGE CONVERTING PANEL
Abstract
The present invention relates to a radiation image converting
panel with a structure capable of arbitrarily controlling the
luminance distribution of the panel surface after formation of a
protective film according to usage conditions. The radiation image
converting panel comprises a support body and a radiation
converting film formed on the support body. The radiation
converting film is formed on a film forming region which existes
within a first main surface of the support body and includes at
least a gravity center position of the first main surface. The film
thickness of the radiation converting film is adjusted such that
the maximum difference can be obtained in either one of a
peripheral area and a middle area from a central area including the
gravity center position.
Inventors: |
SAKURAI; Jun;
(Hamamatsu-shi, JP) ; Shimizu; Ichinobu;
(Hamamatsu-shi, JP) ; Kamimura; Gouji;
(Hamamatsu-shi, JP) |
Correspondence
Address: |
DRINKER BIDDLE & REATH (DC)
1500 K STREET, N.W., SUITE 1100
WASHINGTON
DC
20005-1209
US
|
Assignee: |
HAMAMATSU PHOTONICS K.K.
Hamamatsu-shi
JP
|
Family ID: |
41200330 |
Appl. No.: |
12/350500 |
Filed: |
January 8, 2009 |
Current U.S.
Class: |
250/361R |
Current CPC
Class: |
G01T 1/2921 20130101;
G01T 1/202 20130101; G01T 1/2018 20130101 |
Class at
Publication: |
250/361.R |
International
Class: |
G01T 1/20 20060101
G01T001/20 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 21, 2008 |
JP |
P2008-110369 |
Claims
1. A radiation image converting panel comprising: a support body
having a first main surface and a second main surface opposing said
first main surface; and a radiation converting film provided on a
film forming region which exists within said first main surface of
said support body and includes at least a gravity center position
of said first main surface, said radiation converting film being
comprised of columnar crystals which are coincident or tilted at a
predetermined angle with respect to a normal direction of said
first main surface, wherein, in said film forming region of said
first main surface, a part of said radiation converting film having
a maximum film thickness locates on a central area around the
gravity center position whose radius equals 5% or less of a minimum
distance from the gravity center position to an edge of said film
forming region, and a part of said radiation converting film having
a minimum film thickness locates on a peripheral area sandwiched by
a circumference of a circle whose radius equals 80% of the minimum
distance and the edge of the film forming region.
2. A radiation image converting panel according to claim 1, wherein
the film thickness of said radiation converting film monotonically
decreases from a maximum film thickness point, which is located on
said central area and corresponds to a position where the film
thickness of said radiation converting film is maximized, toward a
minimum film thickness point, which is located on said peripheral
area and corresponds to a position where the film thickness of said
radiation converting film is minimized.
3. A radiation image converting panel according to claim 2,
wherein, when assuming the maximum film thickness point in said
central area as an origin, a distance (>0) from the maximum film
thickness point as a horizontal axis, and a film thickness (>0)
of said radiation converting film at a position corresponding to
the distance from the maximum film thickness point as a
longitudinal axis, a linear line connecting the point that
indicates the maximum film thickness and the point that provides
the minimum film thickness has a gradient of more than -0.002 and
less than 0.
4. A radiation image converting panel according to claim 1, further
comprising a protective film that covers an exposed surface of said
radiation converting film excluding a surface covered by said first
main surface of said support body.
5. A radiation image converting panel comprising: a support body
having a first main surface and a second main surface opposing said
first main surface; and a radiation converting film provided on a
film forming region which exists within said first main surface of
said support body and includes at least a gravity center position
of said first main surface, said radiation converting film being
comprised of columnar crystals which are coindicent or tilted at a
predetermined angle with respect to a normal direction of said
first main surface, wherein, in the film forming region of said
first main surface, a part of said radiation converting film having
a maximum film thickness locates on a central area around the
gravity center position whose radius equals 5% or less of a minimum
distance from the gravity center position to an edge of said film
forming region, and a part of said radiation converting film having
a minimum film thickness locates on a middle area sandwiched by a
circumference of a circle whose radius equals 80% of the minimum
distance and a contour of the central area.
6. A radiation image converting panel according to claim 5, wherein
the film thickness of said radiation converting film located on a
peripheral area, which is sandwiched by the circumference of the
circle defining the middle area and the edge of the film forming
region, monotonically increases from the circumference of the
circle defining the middle area toward the edge of said film
forming region.
7. A radiation image converting panel according to claim 5, further
comprising a protective film that covers an exposed surface of said
radiation converting film excluding a surface covered by said first
main surface of said support body.
8. A radiation image converting panel comprising: a support body
having a first main surface and a second main surface opposing said
first main surface; and a radiation converting film provided on a
film forming region which exists within said first main surface of
said support body and includes at least a gravity center position
of said first main surface, said radiation converting film being
comprised of columnar crystals which are coincident or tilted at a
predetermined angle with respect to a normal direction of said
first main surface, wherein, in the film forming region of said
first main surface, a part of said radiation converting film having
a minimum film thickness locates on a central area around the
gravity center position whose radius equals 5% or less of a minimum
distance from the gravity center position to an edge of said film
forming region, and a part of said radiation converting film having
a maximum film thickness locates on a peripheral area sandwiched by
a circumference of a circle whose radius equals 80% of the minimum
distance and the edge of said film forming region.
9. A radiation image converting panel according to claim 8, wherein
the film thickness of said radiation converting film monotonically
increases from a minimum film thickness point, which is located on
the central area and corresponds to a position where the film
thickness of said radiation converting film is minimized, toward a
maximum film thickness point, which is located on the peripheral
area and corresponds to a position where the film thickness of said
radiation converting film is maximized.
10. A radiation image converting panel according to claim 9,
wherein, when assuming the minimum film thickness point as an
origin, a distance (>0) from the minimum film thickness point as
a horizontal axis, and a film thickness (>0) of said radiation
converting film at a position corresponding to the distance from
the minimum film thickness point as a longitudinal axis, a linear
line connecting the point that indicates the minimum film thickness
and the point that provides the maximum film thickness has a
gradient of more than 0 and less than 0.002.
11. A radiation image converting panel according to claim 8,
further comprising a protective film that covers an exposed surface
of said radiation converting film excluding a surface covered by
said first main surface of said support body.
12. A radiation image converting panel comprising: a support body
having a first main surface and a second main surface opposing said
first main surface; and a radiation converting film provided on a
film forming region which exists within said first main surface of
said support body and includes at least a gravity center position
of said first main surface, said radiation converting film being
comprised of columnar crystals which are coincident or tilted at a
predetermined angle with respect to a normal direction of said
first main surface, wherein, in said film forming region of said
first main surface, a part of said radiation converting film having
a minimum film thickness locates on a central area around the
gravity center position whose radius equals 5% or less of a minimum
distance from the gravity center position to an edge of said film
forming region, and a part of said radiation converting film having
a maximum film thickness locates on a middle area sandwiched by a
circumference of a circle whose radius equals 80% of the minimum
distance and a contour of the central area.
13. A radiation image converting panel according to claim 12,
wherein the film thickness of said radiation converting film
located on a peripheral area, which is sandwiched by the
circumference of the circle that defines the middle area and the
edge of said film forming region, monotonically decreases from the
circumference of the circle that defines the middle area toward the
edge of said film forming region.
14. A radiation image converting panel according to claim 12,
further comprising a protective film that covers an exposed surface
of said radiation converting film excluding a surface covered by
said first main surface of said support body.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a radiation image
converting panel comprising a radiation converting film having a
columnar crystal structure, which converts an incident radiation
ray to a visible light.
[0003] 2. Related Background Art
[0004] Radiation images typified by X-ray images have
conventionally been widely used for a purposes such as disease
diagnosis. As a technique for obtaining such a radiation image, for
example, a radiation image recording and reproducing technique
using a radiation converting film that accumulates and records
irradiated radiation energy, and also emits a visible light
according to radiation energy accumulated and recorded as a result
of irradiating an excitation light has been widely put into
practical use.
[0005] A radiation image converting panel to be applied to such a
radiation image recording and reproducing technique as this
includes a support body and a radiation converting film provided on
the support body. As the radiation converting film, a
photostimulable phosphor layer having a columnar crystal structure
formed by vapor-phase growth (deposition) has been known. When the
photostimulable phosphor layer has a columnar crystal structure,
since a photostimulable excitation light or photostimulable
emission is effectively suppressed from diffusing in the horizontal
direction (reaches the support body surface while repeating
reflection at crack (columnar crystal) interfaces), this allows
remarkably increasing the sharpness of an image by photostimulable
emission.
[0006] For example, Japanese Patent Application Laid-Open No.
H02-58000 has proposed a radiation image converting panel having a
photostimulable phosphor layer for which formed by a vapor-phase
deposition method on a support body are slender columnar crystals
with a constant tilt with respect to a normal direction of the
support body. Furthermore, Japanese Patent Application Laid-Open
No. 2005-315786 has proposed a technique for preventing, by sealing
a photostimulable phosphor layer formed on a support body with a
moisture-proof protective film made of a base material having a
surface roughness Ra of 20 nm or less and a multilayered
moisture-proof layer, deterioration of the photostimulable phosphor
layer due to moisture and the like.
SUMMARY OF THE INVENTION
[0007] The present inventors have examined the conventional
radiation image converting panels in detail, and as a result, have
discovered the following problems. That is, in the conventional
radiation image converting panels, luminance distribution in the
panel surface has changed between before and after formation of a
protective film on the surface of the radiation converting film. As
an example of the change in luminance distribution, specifically,
the luminance in the vicinity of the center of the panel slightly
decreases, while the luminance in the periphery of the panel
increases. Therefore, conventional radiation image converting
panels have had luminance distribution characteristics that the
luminance in the periphery of the panel is higher than that in the
vicinity of the center. In an actual service condition, the
vicinity of the center of the panel is considered to be most
frequently used, and there has been a problem that a luminance
unevenness on the panel surface becomes significant as time
passes.
[0008] The present invention has been developed to eliminate the
problems described above. It is an object of the present invention
to provide a radiation image converting panel with a structure
capable of, in consideration of a change in luminance distribution
of the panel surface between before and after formation of a
protective film to be provided on the surface of a radiation
converting film, arbitrarily controlling the luminance distribution
of the panel surface after formation of a protective film according
to usage conditions.
[0009] A radiation image converting panel according to the present
invention has been completed by the inventors' discovery that
control of the film thickness of a radiation converting film makes
it possible to adjust the luminance of the panel surface after
formation of a protective film. In oncrete terms, a radiation image
converting panel according to the present invention comprises a
support body, and a radiation converting film formed on the support
body. The support body includes a parallel plate having a first
main surface on which the radiation converting film is formed and a
second main surface opposing the first main surface. The radiation
converting film is provided on a film forming region. The film
forming region exists within the first main surface of the support
body and includes at least a gravity center position of the first
main surface. The radiation converting film is an Eu-doped
photostimulable phosphor layer, and is comprised of columnar
crystals which are coincident or tilted at a predetermined angle
with respect to a normal direction of the first main surface.
[0010] Particularly, in the radiation image converting panel
according to the present invention, the radiation converting film
has a sectional shape of any one of a convex sectional shape, a
sectional W-shape, a concave sectional shape, and a sectional
M-shape, in order to arbitrarily control the luminance distribution
of the panel surface after formation of a protective film.
[0011] In the case that the radiation converting film has a convex
sectional shape, in the film forming region of the first main
surface, a part of the radiation converting film having a maximum
film thickness locates on a central area around the gravity center
position whose radius equals 5% or less of a minimum distance from
the gravity center position to an edge of the film forming region,
while a part of the radiation converting film having a minimum film
thickness locates on a peripheral area sandwiched by a
circumference of a circle whose radius equals 80% of the minimum
distance and the edge of the film forming region. Also, when a
radiation converting film having such a convex sectional shape is
adopted, an effect that a luminance distribution of the panel
surface after formation of a protective film becomes flat is
obtained.
[0012] In the case that the radiation converting film has such a
sectional convex shape, the film thickness of the radiation
converting film monotonically decreases from a maximum film
thickness point, which is located on the central area and
corresponds to a position where the film thickness of the radiation
converting film is maximized, toward a minimum film thickness
point, which is located on the peripheral area and corresponds to a
position where the film thickness of the radiation converting film
is minimized. Moreover, when assuming the maximum film thickness
point in the central area, corresponding to a position where the
film thickness of the radiation converting film is maximized, as an
origin, a distance (>0) from the maximum film thickness point as
a horizontal axis, and a film thickness (>0) of the radiation
converting film at a position corresponding to the distance from
the maximum film thickness point as a longitudinal axis, a linear
line connecting the point that indicates the maximum film thickness
and the point that provides the minimum film thickness has a
gradient of more than -0.002 and less than 0.
[0013] In the case that the radiation converting film has a
sectional W-shape, in the film forming region of the first main
surface, a part of the radiation converting film having a maximum
film thickness locates on a central area around the gravity center
position whose radius equals 5% or less of a minimum distance from
the gravity center position to an edge of the film forming region,
while a part of the radiation converting film having a minimum film
thickness locates on a middle area sandwiched by a circumference of
a circle whose radius equals 80% of the minimum distance and a
contour of the central area. Also, in such a sectional W-shape, the
film thickness of the radiation converting film located on a
peripheral area, sandwiched by the circumference of the circle
defining the middle area and the edge of the film forming region,
monotonically increases from the circumference of the circle
defining the middle area toward the edge of the film forming
region. When a radiation converting film having such a sectional
W-shape is adopted, there is an effect, on the panel surface after
formation of a protective film, that the luminance in the vicinity
of the center of the panel can further be increased while entirely
maintaining a luminance equal to or more than an average luminance
of the conventional radiation converting film having a flat
sectional shape.
[0014] Furthermore, in the case that the radiation converting film
has a concave sectional shape, in the film forming region of the
first main surface, a part of the radiation converting film having
a minimum film thickness locates on a central area around the
gravity center position whose radius equals 5% or less of a minimum
distance from the gravity center position to an edge of the film
forming region, while a part of the radiation converting film
having a maximum film thickness locates on a peripheral area
sandwiched by a circumference of a circle whose radius equals 80%
of the minimum distance and the edge of the film forming region.
Also, the radiation converting film having such a concave sectional
shape is effective when an attention imaging region exists in the
periphery of the panel.
[0015] When the radiation converting film has such a concave
sectional shape, the film thickness of the radiation converting
film monotonically increases from a minimum film thickness point,
which is located on the central area and corresponds to a position
where the film thickness of the radiation converting film is
minimized, toward a maximum film thickness point, which is located
on the peripheral area and corresponds to a position where the film
thickness of the radiation converting film is maximized. Moreover,
when assuming the minimum film thickness point in the central area,
corresponding to a position where the film thickness of the
radiation converting film is minimized, as an origin, a distance
(>0) from the minimum film thickness point as a horizontal axis,
and a film thickness (>0) of the radiation converting film at a
position corresponding to the distance from the minimum film
thickness point as a longitudinal axis, a linear line connecting
the point that indicates the minimum film thickness and the point
that provides the maximum film thickness has a gradient of more
than 0 and less than 0.002.
[0016] In the case that the radiation converting film has a
sectional M-shape, in the film forming region of the first main
surface, a part of the radiation converting film having a minimum
film thickness locates on a central area around the gravity center
position whose radius equals 5% or less of a minimum distance from
the gravity center position to an edge of the film forming region,
while a part of the radiation converting film having a maximum film
thickness locates on a middle area sandwiched by a circumference of
a circle whose radius equals 80% of the minimum distance and a
contour of the central area. Also, in such a sectional M-shape, the
film thickness of the radiation converting film located on a
peripheral area, which is sandwiched by the circumference of the
circle defining the middle area and the edge of the film forming
region, monotonically decreases from the circumference of the
circle defining the middle area toward the edge of the film forming
region. When a radiation converting film having such a sectional
M-shape is adopted, an effect to make the effect of the sectional
concave shape described above further prominent is obtained on the
panel surface after formation of a protective film.
[0017] Furthermore, the radiation image converting panel according
to the present invention may include a moisture-resistant
protective film (transparent organic film) that covers an exposed
surface of the radiation converting film excluding a surface
covered by the first main surface of the support body.
[0018] The present invention will be more fully understood from the
detailed description given hereinbelow and the accompanying
drawings, which are given by way of illustration only and are not
to be considered as limiting the present invention.
[0019] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the scope of the invention will be
apparent to those skilled in the art from this detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIGS. 1A to 1C are views showing a structure of an
embodiment of a radiation image converting panel according to the
present invention;
[0021] FIGS. 2A to 2C are views showing sectional structures of
respective parts in a radiation converting film of a radiation
image converting panel according to the present invention;
[0022] FIGS. 3A to 3C are views for concretely explaining a method
for specifying a central area and a peripheral area on the first
main surface of a support body;
[0023] FIGS. 4A and 4E are views for explaining various embodiments
of a radiation converting film in a radiation image converting
panel according to the present invention;
[0024] FIG. 5 is a view showing a configuration of a manufacturing
apparatus for forming, on a support body, a radiation converting
film with a flat surface, as a part of the manufacturing process of
a radiation image converting panel according to the present
invention;
[0025] FIGS. 6A and 6B are views showing a configuration of a
manufacturing apparatus for forming, on a support body, a radiation
converting film with a film thickness reduced from the vicinity of
the center toward the periphery, as a part of the manufacturing
process of a radiation image converting panel according to the
present invention;
[0026] FIGS. 7A and 7B are views showing a configuration of a
manufacturing apparatus for forming, on a support body, a radiation
converting film with a film thickness increased from the vicinity
of the center toward the periphery, as a part of the manufacturing
process of a radiation image converting panel according to the
present invention;
[0027] FIGS. 8A and 8B are a table and a graph showing
relationships between the film thickness and luminance of radiation
converting films;
[0028] FIGS. 9A and 9B are graphs showing relationships between the
distance from the gravity center position and the luminance, with
regard to radiation converting films according to comparative
examples before and after formation of protective films; and
[0029] FIGS. 10A and 10B are graphs showing relationships between
the distance from the gravity center position and the luminance
value, with regard to samples of radiation converting films (each
forming a part of a radiation image converting panel according to
the present invention) before and after formation of protective
films.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] In the following, embodiments of a radiation image
converting panel according to the present invention will be
explained in detail with reference to FIGS. 1A to 4E, 5, and 6A to
10B. In the description of the drawings, identical or corresponding
components are designated by the same reference numerals, and
overlapping description is omitted.
[0031] FIGS. 1A to 1C are views showing a structure of an
embodiment of a radiation image converting panel according to the
present invention. In particular, FIGS. 1A is a plan view of the
radiation image converting panel 1, FIG. 1B is a sectional view of
the radiation image converting panel 1 along the line I-I in FIG.
1A, and FIG. 1C is a sectional view of the radiation image
converting panel 1 along the line II-II in FIG. 1A.
[0032] In FIGS. 1A to 1C, the radiation image converting panel 1
comprises a support body 100, a radiation converting film 200
formed on the support body 100, and a protective film 300
(transparent organic film) that wholly covers the support body 100
and the radiation converting film 200. The support body 100 is a
parallel plate having a first main surface 100a on which the
radiation converting film 200 is formed and a second main surface
100b opposing the first main surface 100a. Moreover, when the
support body 100 is made of a corrodible metal material such as Al,
an anti-corrosion film such as an anodic oxidation film is
preferably formed on the surface thereof. The radiation converting
film 200 is formed on a film forming region R. The film forming
region R exists within the first main surface 100a of the support
body 100 and includes at least a gravity center position G of the
first main surface 100a. This radiation converting film 200 is
comprised of columnar crystals which are coincident or tilted at a
predetermined angle with respect to a normal direction of the first
main surface 100a.
[0033] FIGS. 2A to 2C are views showing sectional structures of
respective parts in a radiation converting film according to the
present invention. In concrete terms, FIG. 2A is a sectional view
of a region A1 in FIG. 1C, FIG. 2B is a sectional view of a region
B1 in FIG. 1C, and FIG. 2C is a sectional view of a region C1 in
FIG. 1C.
[0034] As can be understood from FIGS. 2A to 2C, the crystal
diameters D1 to D3 of columnar crystals that form the radiation
converting film 200 are all approximately 7 .mu.m, which are almost
uniform across the entire surface of the radiation converting film
200. However, the radiation converting film 200 has been doped with
Eu being an activator, and for the film thickness of the radiation
converting film 200, in consideration of a change in luminance
distribution between before and after formation of a protective
film 300, the sectional shape is adjusted so as to meet a specific
purpose.
[0035] Next, by use of FIGS. 3A to 3C, description will be given,
in terms of a film forming region R in the first main surface 100a
of the support body 100, of a central area AR1, a peripheral area
AR2, and a middle area AR3 of the film forming region R for
defining a film thickness distribution of the radiation converting
film 200 to be formed on the film forming region R. FIG. 3A is a
view for concretely explaining a method for specifying a central
area AR1 and a peripheral area AR2 in the first main surface 100a
(film forming region R) of the support body 100.
[0036] As shown in FIG. 3A, the central area AR1 in the film
forming region R is a local region including the gravity center
position G. In concrete terms, this is a local region including the
gravity center position G whose radius equals 5% of a minimum
distance W.sub.min from the gravity center position G to an edge of
the film forming region R. Accordingly, a distance from the gravity
center position G to a contour of the central area AR1 is given by
W.sub.0.05. On the other hand, the peripheral area AR2 in the film
forming region R is a local region sandwiched by the edge of the
film forming region R and the circumference of a circle whose
radius equals 40% to 80% of the minimum distance W.sub.min from the
gravity center position G to an edge of the film forming region R.
The radius is given at this time by a distance W.sub.0.8 (when the
distance is 80% of the minimum distance W.sub.min) from the gravity
center position G to the circumference. Moreover, the middle area
AR3 is a region sandwiched by the contour of the central area AR1
and the circumference of the circle to define the peripheral area
AR2.
[0037] Also, the radiation converting film 200 is formed on the
film forming region R of the first main surface 100a where the
central area AR1, the peripheral area AR2, and the middle area AR3
are thus defined, and the vicinity of the center and periphery of
the radiation converting film 200 may be considered as regions
substantially coincident with the central area AR1 and the
peripheral area AR2 defined in FIG. 3A, respectively.
[0038] The radiation converting film 200 has a sectional shape (for
example, a section along the line II-II in FIG. 1A) of any one of a
convex sectional shape, a sectional W-shape, a concave sectional
shape, and a sectional M-shape, in order to arbitrarily control the
luminance distribution of the panel surface after formation of the
protective film 300.
[0039] Particularly, in the case that the radiation converting film
200 has a convex sectional shape, as shown in, for example, FIG.
3B, the film thickness monotonically decreases from a maximum film
thickness point, which is located on the central area AR1 and
corresponds to a position where the film thickness of the radiation
converting film 200 is maximized (for example, the gravity center
position G), toward a minimum film thickness point, which is
located on the peripheral area AR2 and corresponds to a position
where the film thickness of the radiation converting film 200 is
minimized (for example, a position where a distance from the
gravity center position G is W.sub.0.8). Also, FIG. 3B is a graph
showing a relationship between the distance and a change in film
thickness, wherein the maximum film thickness point, which is
located on the central area AR1 and corresponds to the gravity
center position G where the film thickness of the radiation
converting film 200 is maximized, is assumed as the origin, a
distance (>0) from the maximum film thickness point is assumed
as the horizontal axis, and a film thickness (>0) of the
radiation converting film 200 at a position corresponding to the
distance from the maximum film thickness point is assumed as the
longitudinal axis.
[0040] The support body 100 assumes a minimum size of 100
mm.times.100 mm and a maximum size of 1000 mm.times.1000 mm. At
this time, the radiation converting film 200 has a film thickness
of 100 .mu.m to 1100 .mu.m. When reading a radiation image
accumulated in a photostimulable phosphor layer serving as the
radiation converting film 200 by a scanner, for avoiding a
deterioration in the S/N ratio whenever possible, an allowable
range of variation in film thickness of the radiation converting
film 200 is .+-.100 .mu.m, preferably, .+-.180 .mu.m (when a
variation in film thickness of the entire surface of the film
forming region R is provided as .+-.100 .mu.m at a maximum, .+-.80
.mu.m at a position of the distance W.sub.0.8).
[0041] In concrete terms, when the support body 100 has a size of
100 mm.times.100 mm (the film forming region R has a slightly
smaller size), the film thickness at the position separated from
the gravity center position G by the distance W.sub.0.8 (the
minimum distance W.sub.min is 50 mm, and a distance that equals 80%
thereof is 40 mm) is reduced by 80 .mu.m at a maximum from the film
thickness of the radiation converting film 200 at the gravity
center position G. At this time, a gradient "a" of the graph shown
in FIG. 3B is -0.0002 (=-0.008 mm/40 mm). Accordingly, when the
radiation converting film 200 has a convex sectional shape, the
gradient "a" of the graph showing a change in film thickness
(monotonic decrease) satisfies -0.002<a<0.
[0042] On the other hand, in the case that the radiation converting
film 200 has a concave sectional shape, as shown in, for example,
FIG. 3C, the film thickness monotonically increases from a minimum
film thickness point, which is located on the central area AR1 and
corresponds to a position where the film thickness of the radiation
converting film 200 is minimized (for example, the gravity center
position G), toward a maximum film thickness point, which is
located on the peripheral area AR2 and corresponds to a position
where the film thickness of the radiation converting film 200 is
maximized (for example, a position where a distance from the
gravity center position G is W.sub.0.8). Also, FIG. 3C is a graph
showing a relationship between the distance and a change in film
thickness, wherein the minimum film thickness point, which is
located on the central area AR1 and corresponds to the gravity
center position G where the film thickness of the radiation
converting film 200 is minimized, is assumed as the origin, a
distance (>0) from the minimum film thickness point is assumed
as the horizontal axis, and a film thickness (>0) of the
radiation converting film 200 at a position corresponding to the
distance from the minimum film thickness point is assumed as the
longitudinal axis.
[0043] For calculating a gradient "b" of the graph shown in FIG. 3C
under the same conditions as those in the case of FIG. 3B, when the
support body 100 has a size of 100 mm.times.100 mm (the film
forming region R has a slightly smaller size), the film thickness
at the position separated from the gravity center position G by the
distance W.sub.0.8 (the minimum distance W.sub.min is 50 mm, and a
distance that equals 80% thereof is 40 mm) is increased by 80 .mu.m
at a maximum from the film thickness of the radiation converting
film 200 at the gravity center position G. At this time, a gradient
"b" of the graph shown in FIG. 3C is 0.0002 (=0.008 mm/40 mm).
Accordingly, when the radiation converting film 200 has a concave
sectional shape, the gradient "b" of the graph showing a change in
film thickness (monotonic increase) satisfies 0<b<0.002.
[0044] Next, description will be given of a concrete sectional
structure of the radiation converting film 200 to be applied to the
radiation image converting panel 1 according to the present
invention. FIGS. 4A and 4B are views for explaining various
embodiments of the radiation converting film in a radiation image
converting panel 1 according to the present invention. The sections
shown in FIGS. 4A to 4E are sectional views along the line II-II in
FIG. 1A. Also, FIG. 4A is a sectional view of a radiation image
converting panel having a radiation converting film formed so that
the film thickness becomes uniform, prepared for a comparison.
[0045] The radiation image converting panel according to a
comparative example shown in FIG. 4A includes a radiation
converting film having a flat sectional shape without a change in
film thickness between the vicinity of the center and periphery.
Such a radiation image converting panel showed a sharp drop in
luminance in the vicinity of the center of the panel after
formation of a protective film, and a luminance unevenness occurred
in the panel as a whole (see FIGS. 9A and 9B to be described
later).
[0046] FIG. 4B is a sectional view of the radiation image
converting panel 1 according to the present invention, which
includes a radiation converting film 200 having a convex sectional
shape. In the case that a radiation converting film 200 having such
a convex sectional shape is adopted, an effect that a luminance
distribution of the panel surface after formation of a protective
film becomes flat is obtained.
[0047] In the radiation converting film 200 having a convex
sectional shape, a part of the radiation converting film 200 having
the maximum film thickness locates on the central area AR1, while a
part of the radiation converting film 200 having the minimum film
thickness locates on the peripheral area AR2. A change in film
thickness at this time is represented by a monotonic decreasing
function with a gradient "a" that satisfies -0.002<a<0, as
shown in FIG. 3B.
[0048] FIG. 4C is a sectional view of the radiation image
converting panel 1 according to the present invention, which
includes a radiation converting film 200 having a sectional
W-shape. In the case that a radiation converting film 200 having
such a sectional W-shape is adopted, there is an effect, on the
panel surface after formation of a protective film, that the
luminance in the vicinity of the center of the panel can further be
increased while wholly maintaining a luminance equal to or more
than an average luminance of the radiation converting film 200
having a flat sectional shape in FIG. 4A.
[0049] In the radiation converting film 200 having a sectional
W-shape, a part of the radiation converting film 200 having the
maximum film thickness exists on the central area AR1, while a part
of the radiation converting film 200 having the minimum film
thickness locates on the middle area AR3. Moreover, the film
thickness of the radiation converting film 200 located on the
peripheral area AR2 monotonically increases from the middle area
AR3 toward the edge of the film forming region R.
[0050] FIG. 4D is a sectional view of the radiation image
converting panel 1 according to the present invention, which
includes a radiation converting film 200 having a concave sectional
shape. In the case that a radiation converting film 200 having such
a concave sectional shape is adopted, an effect that the luminance
in the periphery of the panel is increased is obtained on the panel
surface after formation of a protective film. The radiation
converting film 200 having such a concave sectional shape is
effective when an attention imaging region exists in the periphery
of the panel.
[0051] In the radiation converting film 200 having a sectional
concave shape, a part of the radiation converting film 200 having
the minimum film thickness exists on the central area AR1, while a
part of the radiation converting film 200 having the maximum film
thickness locates on the peripheral area AR2. A change in film
thickness at this time is represented by a monotonic increasing
function with a gradient "b" that satisfies 0<b<0.002, as
shown in FIG. 3C.
[0052] FIG. 4E is a sectional view of the radiation image
converting panel 1 according to the present invention, which
includes a radiation converting film 200 having a sectional
M-shape. In the case that a radiation converting film 200 having
such a sectional M-shape is adopted, an effect to make the effect
of the sectional concave shape shown in FIG. 4D further prominent
is obtained on the panel surface after formation of a protective
film.
[0053] In the radiation converting film 200 having a sectional
M-shape, a part of the radiation converting film 200 having the
minimum film thickness exists on the central area AR1, while a part
of the radiation converting film 200 having the maximum film
thickness locates on the middle area AR3. Moreover, the film
thickness of the radiation converting film 200 on the peripheral
area AR2 monotonically decreases from the middle area AR3 toward
the edge of the film forming region R.
[0054] The radiation image converting panel 1 according to the
present invention, specifically, the radiation converting film 200
provided on the support body 100 is formed by a manufacturing
apparatus shown in any one of FIGS. 5 and 6A to 7B. More
specifically, by controlling the position to install a phosphor
evaporation source and the inflow direction of a metal vapor in
each of the manufacturing apparatuses shown in FIGS. 5 and 6A to
7B, the radiation converting films 200 having various sectional
structures as shown in FIGS. 4B to 4E are obtained.
[0055] First, FIG. 5 is a view showing a configuration of a
manufacturing apparatus 10a for forming, on the support body 100, a
radiation converting film 200 with a flat surface (a flat sectional
shape), as a part of the manufacturing process of the radiation
image converting panel 1 according to the present invention.
[0056] The manufacturing apparatus 10a shown in FIG. 5 is an
apparatus that forms a radiation converting film 200 on the first
main surface 100a of the support body 100 by a vapor-phase
deposition method. As the vapor-phase deposition method, a vapor
deposition method, a sputtering method, a CVD method, an ion
plating method, or the like is applicable, and description will be
given for, as an example, a case where the radiation converting
film 200 of Eu-doped CsBr is formed on the support body 100 by a
vapor deposition method. This manufacturing apparatus 10a includes,
at least, a vacuum container 11, a support body holder 14, a rotary
shaft 13a, a drive unit 13, a phosphor evaporation source 15, and a
vacuum pump 12. The support body holder 14, the evaporation source
15, and a part of the rotary shaft 13a are arranged in the vacuum
container 11. The support body holder 14 includes a heater 14a to
heat the support body 100. One end of the rotary shaft 13a extended
from the drive unit 13 is attached to the support body holder 14,
and the drive unit 13 rotates the support body holder 14 via the
rotary shaft 13a. The phosphor evaporation source 15, which is
arranged at a position deviated from a center axis AX of the vacuum
container 11, holds a metal material supplied as a metal vapor to
be vapor-deposited on the support body 100 installed on the support
body holder 14. The vacuum pump 12 depressurizes the interior of
the vacuum container 11 to a predetermined degree of vacuum.
[0057] In the phosphor evaporation source 15, a mixture material of
CsBr and EuBr is set. Moreover, the phosphor evaporation source 15
is set so that the inflow direction of a metal vapor points to the
middle area AR3 of the support body 100 from the position off the
axis AX. The support body 100 is set on the support body holder 14.
The crystal diameter of columnar crystals to be formed on a
surface, of the support body 100, facing the phosphor evaporation
source 15 is adjusted by adjusting the temperature of the support
body 100 itself with the heater 14a, and by controlling the degree
of vacuum in the vacuum container 11, an inflow angle of the metal
vapor from the material source 15 to the support body 100, and the
like.
[0058] First, columnar crystals of Eu-doped CsBr are grown on the
first main surface 100a (the surface facing the phosphor
evaporation source 15) of the support body 100 by a vapor
deposition method. At this time, the drive unit 13 is rotating the
support body holder 14 via the rotary shaft 13a, and accordingly,
the support body 100 is also rotating around the axis AX.
[0059] By such a vapor deposition method, a radiation converting
film 200 with a film thickness of 500 .mu.m.+-.50 .mu.m is formed
on the support body 100. At this time, the crystal diameter of
columnar crystals of the radiation converting film 200 is
approximately 3 .mu.m to 10 .mu.m on average.
[0060] FIGS. 6A and 6B are views showing a configuration of a
manufacturing apparatus 10b for forming, on the support body 100, a
radiation converting film 200 with a film thickness reduced from
the vicinity of the center toward the periphery (a convex sectional
shape), as a part of the manufacturing process of the radiation
image converting panel 1 according to the present invention. The
manufacturing apparatus 10b shown in FIGS. 6A and 6B differs from
the manufacturing apparatus 10a shown in FIG. 5 in terms of
arrangement of the phosphor evaporation source 15 and inflow
direction of a metal vapor.
[0061] More specifically, in the manufacturing apparatus 10b shown
in FIG. 6A, the phosphor evaporation source 15 is installed at a
position off the axis AX, and the inflow direction of a metal vapor
from the phosphor evaporation source 15 is oriented to the middle
area AR3 located at an opposite side across the axis AX in a manner
crossing the axis AX. As a result of the phosphor evaporation
source 15 being thus installed, a radiation converting film 200
having a convex sectional shape as shown in FIG. 4B is formed on
the first main surface 100a of the support body 100. Meanwhile,
FIG. 6B discloses only a main part of FIG. 6A, which differs from
the case of FIG. 6A in position to install the phosphor evaporation
source 15. That is, in the apparatus 10b shown in FIG. 6B, the
inflow direction of a metal vapor from the phosphor evaporation
source 15 is oriented to the central area AR1 of the support body
100. Thus, as a result of the phosphor evaporation source 15 being
installed as shown in FIG. 6B as well, a radiation converting film
200 having a convex sectional shape as shown in FIG. 4B is
obtained.
[0062] Furthermore, FIGS. 7A and 7B are views showing a
configuration of a manufacturing apparatus 10c for forming, on the
support body 100, a radiation converting film 200 with a film
thickness increased from the vicinity of the center toward the
periphery (a concave sectional shape), as a part of the
manufacturing process of the radiation image converting panel 1
according to the present invention. The manufacturing apparatus 10c
shown in FIGS. 7A and 7B differs from the manufacturing apparatuses
10a and 10b shown in FIGS. 5, 6A, and 6B in terms of arrangement of
the phosphor evaporation source 15 and inflow direction of a metal
vapor.
[0063] More specifically, in the manufacturing apparatus 10c shown
in FIG. 7A, the phosphor evaporation source 15 is installed in the
vicinity of the support body 100, and the inflow direction of a
metal vapor from the phosphor evaporation source 15 is oriented to
the peripheral area AR2 of the support body 100 (namely, the edge
of the support body 100). As a result of the phosphor evaporation
source 15 being thus installed, a radiation converting film 200
having a concave sectional shape as shown in FIG. 4D is formed on
the first main surface 100a of the support body 100. Meanwhile,
FIG. 7B discloses only a main part of FIG. 7A, which differs from
the case of FIG. 7A in position to install the phosphor evaporation
source 15. That is, in the apparatus 10c shown in FIG. 7B, the
phosphor evaporation source 15 is installed in a manner separated
from the support body 100 further than in the case of FIG. 7A,
while the inflow direction of a metal vapor therefrom is oriented
to the edge of the support body 100 as in the case of FIG. 7A.
Thus, as a result of the phosphor evaporation source 15 being
installed as shown in FIG. 7B as well, a radiation converting film
200 having a concave sectional shape as shown in FIG. 4D is
obtained.
[0064] Also, in the case that the radiation converting films 200
having such special sectional shapes as in FIGS. 4C and 4E are
formed, it suffices to combine the evaporation source arrangements
shown in FIG. 5 and 6A to 7B described above. For example, the
radiation converting film 200 having a sectional W-shape shown in
FIG. 4C is obtained by combining the arrangement for a sectional
convex shape shown in FIG. 6A or 6B and the arrangement for a
sectional concave shape shown in FIG. 7A or 7B. In addition, the
radiation converting film 200 having a sectional M-shape shown in
FIG. 4E is obtained by combining the arrangement for a flat
sectional shape shown in FIG. 5 and the arrangement for a sectional
convex shape (where the inflow direction of a metal vapor being off
the center of the support body 100) shown in FIG. 6A or 6B.
[0065] The CsBr being a material of the radiation converting film
200 formed on the support body 100 by any one of the manufacturing
apparatuses 10a to 10c of FIGS. 5 and 6A to 7B or combining these
as described above is highly hygroscopic. The radiation converting
film 200 absorbs vapor in the air to deliquesce when this is kept
exposed. Therefore, subsequent to the forming step of the radiation
converting film 200 by a vapor deposition method, a
moisture-resistant protective film 300 is formed by a CVD method so
as to cover an entire exposed surface of the radiation converting
film 200. More specifically, the support body 100 on which the
radiation converting film 200 has been formed is placed in a CVD
apparatus, and a moisture-resistant protective film 300 with a film
thickness of approximately 10 .mu.m is formed on the exposed
surface of the radiation converting film 200. Thereby, the
radiation image converting panel 1 for which the moisture-resistant
protective film 300 has been formed on the radiation converting
film 200 and the support body 100 is obtained.
[0066] Next, description will be given of a relationship between
film thickness control and a change in luminance of the radiation
converting film 200. FIGS. 8A and 8B are a table and a graph
showing relationships between the film thickness and luminance of
the radiation converting films 200. FIG. 8A is a table showing
numerical values when radiation converting film samples having
various film thicknesses (.mu.m) were prepared and respective
luminances were measured. In FIG. 8A, the luminances are shown as
relative values (standardized values with the maximum value
provided as 1). FIG. 8B is a graph plotting the relationships
between the film thickness and luminance relative value shown in
FIG. 8A.
[0067] As can be understood from FIG. 8B, the radiation converting
films generally have a tendency that as the film thickness
increases, the luminance also increases. It can be understood from
this that individually adjusting the film thicknesses of arbitrary
regions of the radiation converting film 200, the luminance
distribution of the panel surface can be adjusted according to
usage conditions. In the following, referring to FIGS. 9A to 10B,
effects of luminance distribution control by the present invention
will be concretely described.
[0068] FIGS. 9A and 9B are graphs showing relationships between the
distance from the gravity center position and the luminance, with
regard to radiation converting films according to comparative
examples before and after formation of protective films. Two
samples of radiation converting films prepared as the comparative
examples have flat sectional shapes. FIG. 9A is a graph showing a
relationship between the measuring position (displayed as the
distance from the gravity center position) and the relative
luminance value, with regard to two prepared samples according to
the comparative examples before formation of protective films.
Also, FIG. 9B is a graph showing a relationship between the
measuring position and the relative luminance value, with regard to
two prepared samples according to the comparative examples after
formation of protective films. These two samples according to the
comparative examples had, before formation of protective films, a
ratio of the amount of variation (maximum luminance value minus
minimum luminance value) with reference to the maximum luminance
value of 2.7%. However, after formation of protective films, for
the two samples according to the comparative examples, the ratio of
the amount of variation (maximum luminance value minus minimum
luminance value) with reference to the maximum luminance value has
increased to 5.6%. In particular, as can be understood from FIG.
9B, a drop in luminance in the vicinity of the center of the panel
was significant.
[0069] In contrast thereto, FIGS. 10A and 10B are graphs showing
relationships between the distance from the gravity center position
and the luminance value, with regard to radiation converting films
(each forming a part of a radiation image converting panel
according to the present invention) before and after formation of
protective films. Two samples of the radiation converting films 200
to be applied to the radiation image converting panels 1 according
to the present invention have convex sectional shapes. FIG. 10A is
a graph showing a relationship between the measuring position
(displayed as the distance from the gravity center position) and
relative luminance value, with regard to two prepared samples
before formation of protective films. Also, FIG. 10B is a graph
showing a relationship between the measuring position and the
relative luminance value, with regard to two samples after
formation of protective films. These two samples had, before
formation of protective films, a large ratio of the amount of
variation (maximum luminance value minus minimum luminance value)
with reference to the maximum luminance value, that is, 6.0%.
However, for the two samples after formation of protective films,
the ratio of the amount of variation (maximum luminance value minus
minimum luminance value) with reference to the maximum luminance
value has reduced to 3.2%. In particular, as can be understood from
FIG. 10B, as a result of the radiation ray converting films having
convex sectional shapes being applied, the luminance of the panel
surfaces after formation of protective films is further improved in
uniformity.
[0070] As in the above, according to the present invention, it
becomes possible, in consideration of a change in luminance
distribution of the panel surface between before and after
formation of a protective film to be provided on the surface of a
radiation converting film, to arbitrarily control the luminance
distribution of the panel surface after formation of a protective
film according to usage conditions, such as making the luminance of
the panel surface as a whole uniform, or increasing luminance in
only a specific attention region.
[0071] From the invention thus described, it will be obvious that
the embodiments of the invention may be varied in many ways. Such
variations are not to be regarded as a departure from the scope of
the invention, and all such modifications as would be obvious to
one skilled in the art are intended for inclusion within the scope
of the following claims.
* * * * *